As typified by S3G (Super 3G), a communication system in which base stations are connected to each other through multiple data-paths by using a multi-homing method, has been put into practical use. For example, Japanese Laid-Open Patent Application Publication No. 2000-209278 and 2006-279467 disclose about a communication system in which a multi-homing method is employed. According to a multi-homing method, a network within a company can be connected to another network outside the company through a plurality of data-paths, for example, using a plurality of ISPs (Internet Service Providers).
According to a multi-homing method, a communication apparatus, such as a base station, is typically configured to include a card for handling SCTP (Stream Control Transmission Protocol) which is a protocol corresponding to a transmission layer. The card may have, for example, two link ports each connected to a link port of another communication apparatus with which the base station communicates. The card may be configured to include a SCTP handler that terminates a SCTP signal. In the case, one of the two link ports is used for a primary data-path and the other one for a secondary data-path where a global address is assigned to each of the two link ports. Data is transmitted and received through the primary data-path under normal conditions, and the secondary data-path is used as an alternate path when the primary data-path is disconnected, for example, due to a failure. Here, it is also possible to distribute a communication load by using both the primary and secondary data-paths concurrently.
However, in the case where a card has only one link port for communicating with another communication apparatus, the above mentioned multi-homing communication may not be attained. Therefore, to perform a multi-homing communication, each of primary and secondary data-paths needs to be accommodated in a different card. Further, a communication apparatus, such as a base station, may be configured to include a redundant card so as to keep communication even if a failure has occurred in some cards. Adopting a redundant card requires each of primary and secondary data-paths to be accommodated in a different card. However, if each of primary and secondary data-paths is accommodated in a different card, a multi-homing method may not be applied since the primary and secondary data-paths are handled independently by each of SCTP handlers of two different cards.
In order to avoid the above problem, it may be possible to configure an access controller of the card, which is normally configured to provide services such as call processing, to perform a multi-homing communication. However, this causes another problem that the load of the access controller becomes higher, thereby exerting an adverse effect on providing the above-mentioned services such as call processing.
Further, in the case of a card having only one link port for communicating with another communication apparatus, the card may be assigned with one global address and one local address. A multi-homing method according to SCTP uses two global addresses each assigned to one of primary and secondary data-paths. In this case, when a setting for a multi-homing communication has been done within the card, the SCTP handler of the card may try to start a communication with another communication apparatus using both the global address and the local address which are assigned to the card. However, the communication using the local address fails since the local address is effective only within the communication apparatus. As a result, a multi-homing communication with another communication apparatus may not be performed. This case is also undesirable from the aspect of security because the local address for the card of the communication apparatus may flow out into the network.